The goal is to get humans to Mars by the mid-2030s, but what are the stepping stones that will get us there? Returning to the Moon gets a lot of publicity, but the better test might be a near-Earth asteroid.

Space.com columnist Leonard David has an intriguing feature on Lockheed Martin's research into sending astronauts to a near-Earth asteroid by the mid-2020s. Nicknamed the "Plymouth Rock" mission, landing on an asteroid wouldn't only be a great dress rehearsal for the long trip to Mars; it could also allow us to set up planetary defenses against asteroid impacts. (Armageddon is turning into a documentary so slowly, no one's even noticing.)

He quotes Lockheed Martin's Josh Hopkins, who explains just how close we are to sending humans to asteroids:

"We expected asteroid missions to be thoroughly difficult and further in the future. What we discovered is that they are within reach of the technologies that we're ready to field today. We could do an asteroid mission within a decade. I think we're a lot more likely to succeed if we get started and fly sooner rather than later."